1. Field of the Invention
The present invention relates, in general, to the desulfurization of flue gas and, in particular, to a new and useful atomizer cap for a dry scrubber reactor which utilizes an expandable diaphragm.
2. Description of the Related Art
Dry flue gas desulfurization systems such as dry scrubber reactors (DSR's) operate by atomizing an aqueous sorbent (slurry or solution or solids containing fluid) into a reaction chamber containing hot flue gas, where sulfur dioxide (SO.sub.2) in the flue gas reacts with the sorbent and dries into a powder. Similar systems such as humidification systems are used to atomize water which contains small amounts of suspended or dissolved solids into a flue gas. The primary methods for atomizing the fluid employ either rotary atomizers or dual-fluid atomizers. One known dual-fluid atomizer is sold by Babcock & Wilcox under the trademark Durajet.TM. which is a dual-fluid type atomizer which has replaced the maintenance-intensive rotary atomizers in some applications.
Dual-fluid atomizer jets entrain surrounding gas that contains a portion of the atomized fluid. The entrained gas flow subsequently establishes a recirculation zone near the atomizer with regions of reverse gas flow. This reverse flow causes fluid droplets to impinge onto the exterior surface of the atomizer end cap. This wetting of the atomizer is known as spray-back. As the water evaporates from the wet atomizer, deposits are formed. If not removed, deposition continues until interference occurs with the atomized jets discharged through the exit orifices, which degrades and deteriorates atomizer performance.
The aircraft industry has used inflatable bladders on critical surfaces of wings for shedding the build-up of ice while in flight.
Presently, the spray-back condition is alleviated by supplying shield air as an annular flow around the atomizer. The shield air is aimed at preventing droplets in the recirculating flow from impinging on the atomizer. Testing of known atomizers with water and air as the working fluids has shown that the shield air helps to minimize spray-back onto the end cap, but does not prevent end cap wetting downstream of the exit orifices of the atomizer. Moreover, high shield air flow rates can distort the spray pattern, further wetting the end cap, which leads to greater deposit growth in an operating DSR system.